The desktop example with the 2.0 trunk code gets exceptions like the following while open/close/switch windows.

java.lang.NullPointerException: null
at com.extjs.gxt.desktop.client.Desktop.markActive(Desktop.java:249)
at com.extjs.gxt.desktop.client.Desktop.access$0(Desktop.java:242)
at com.extjs.gxt.desktop.client.Desktop$2.windowActivate(Desktop.java:196)